Erector Spinae
The erector spinae is a group of muscles and tendons running along the spine from the sacrum to the skull. It consists of three columns (iliocostalis, longissimus, spinalis) that extend and stabilize the vertebral column.
Origin, Insertion, Action, Innervation
OOrigin
Sacrum, iliac crest, spinous and transverse processes of vertebrae
IInsertion
Ribs, transverse and spinous processes of vertebrae, mastoid process (longissimus capitis)
AAction
- • Extension of the vertebral column (bilateral contraction)
- • Lateral flexion of the vertebral column (unilateral contraction)
- • Maintenance of upright posture
- • Control of trunk flexion (eccentric contraction)
NInnervation
Posterior rami of spinal nerves
Blood Supply
Posterior intercostal arteries, lumbar arteries
Clinical Relevance
Erector spinae strain is a common cause of lower back pain. The muscles work eccentrically when bending forward to control the descent. Weakness or imbalance can contribute to postural problems and spinal instability.
Palpation
Palpate along both sides of the spine. Have the patient extend the back against resistance to feel the muscles contract.
Study Tips
- ✓Three columns: I Love Spine (Iliocostalis, Longissimus, Spinalis) - lateral to medial
- ✓Innervated by posterior rami (unlike most muscles which use anterior rami)
- ✓Work eccentrically when bending forward (controlled lowering)
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Common questions about the erector spinae
The erector spinae consists of three columns from lateral to medial: iliocostalis (attached to ribs), longissimus (longest, attached to transverse processes), and spinalis (attached to spinous processes).
The erector spinae maintains the normal curves of the spine and keeps the trunk upright against gravity. It constantly activates during standing and sitting to prevent forward flexion of the trunk.
Erector spinae strain commonly occurs from lifting heavy objects with poor form, prolonged sitting with poor posture, or sudden twisting movements. It is a major cause of lower back pain.
When bending forward, the erector spinae contracts eccentrically (lengthening while generating force) to control the descent. This is why lifting with a rounded back can strain these muscles.